JP6931276B2 - Thermally efficient electrical assembly - Google Patents

Description

The present invention relates to a thermally efficient electrical assembly for optimizing heat transfer or dissipation from electrical components. The present invention further relates to a flexible circuit preferably having a high thermal efficiency, and more preferably a lighting component including such a flexible circuit having such a high thermal efficiency.

The generation of heat from electrical components can adversely affect its usefulness, especially its efficiency and longevity. Essentially more efficient components have been developed to reduce residual heat, but advances in technology that enable such improvements will result in the development of smaller, higher performance components.

One such example is a light emitting diode or LED. LEDs are advantageously much more energy efficient than incandescent bulbs of the same brightness, but in the early days of their development, LEDs had low power and were limited in use in many situations. However, LEDs and related technologies have advanced to the point where LEDs have now replaced incandescent bulbs or other light sources in high power applications such as floodlights and vehicle headlight clusters. However, the improvement of LED brightness leads to the generation of a large amount of residual heat, and this heat needs to be efficiently dissipated in order to increase the efficiency and life of the component.

In many applications, LEDs and other heat-generating electrical components are required to be mounted directly on a circuit board. Therefore, it is common to install heat sinks on these circuit boards or in direct contact with them. However, the structure of the circuit board may contribute to insufficient heat dissipation. In particular, adhesives are commonly used to join layers of circuit boards.

The adhesive provides electrical insulation between the layers of the circuit board. This is especially necessary when used with a heatsink, as it is important to avoid short circuits of any electrical circuit through a heatsink, which is generally made of metal. Unfortunately, adhesives generally have poor thermal energy conductivity compared to other materials and may eventually act as a partial insulator.

Therefore, in order to dissipate residual heat from electrical components, it is necessary to develop a circuit board structure with higher thermal efficiency. By doing so, more efficient long-life parts can be made possible.

An object of the present invention is to prevent or alleviate the above-mentioned problems by mounting an electric assembly having high thermal efficiency.

According to the first aspect of the present invention, a conductive layer, a heat sink layer, an electrically insulating interconnect layer inserted between the conductive layer and the heat sink layer, an electric component that electrically communicates with the conductive layer, and an electric component. A thermally efficient electrical assembly is provided that comprises a metal thermal bridge that thermally communicates with electrical components and is in direct contact with the heat sink layer, bypassing the electrically insulating interconnect layer by the metal thermal bridge.

The present invention provides an efficient thermal path from electrical components to the heat sink layer via intervening materials. Therefore, heat transfer is optimized, allowing electrical components to operate more efficiently and for longer periods of time.

In a preferred embodiment, the electrically insulating interconnect layer can be an electrically insulating adhesive layer. Such a layer can promote adhesion between the conductive layer and the heat sink.

Preferably, the heat sink layer can include upper and lower heat sink sublayers, the upper heatsink sublayer being adhered to the conductive layer. In this case, by forming the heat sink layer with a plurality of sublayers, it is possible to optimize the thermal characteristics by changing the characteristics of each layer.

Conveniently, copper is a good thermal conductor and the upper heat sink sublayer can be composed of copper. In addition, copper has the property of allowing easy and strong bonding between itself and other metals such as solder.

Further advantages can be gained by the lower heat sink sublayer made of aluminum. Aluminum is a very effective radiator in addition to being a similarly good conductor, which is convenient for forming a part of the heat sink. Aluminum is even lighter, ensuring that the heat sink does not have an excessively large mass.

In a preferred embodiment, the conductive layer can be further adhered to the substrate layer.

The substrate layer can provide additional strength and / or flexibility to the assembly. The substrate layer can also serve as an additional electrically insulating layer to prevent any unwanted electrical conduction through the circuit board.

Conveniently, the substrate layer can include polyimide. Polyimides have good strength and flexibility, many of which are flame retardant. In addition, polyimide is chemically stable and, in addition, is electrically insulating. Each of these properties is favorable for circuit board assemblies.

Preferably, the metal thermal bridge can include solder. Solder is easy to apply, has good thermal conductivity, and bonds well with other metals such as copper. Therefore, solder is suitable for use as a thermal bridge. However, other suitable materials can be considered, if desired.

More preferably, the metal thermal bridge can be solder rivets. In this case, by riveting the solder, the heat conduction between each component can be increased by increasing the contact area.

In a desirable configuration, the electrical component can include a thermal pad and preferably a metal thermal bridge in direct contact with both the thermal pad and the heat sink layer.

The thermal pad provides an electrically isolated portion of the component for heat transfer. A more efficient heat path can then be utilized by connecting this portion directly to the heat sink layer.

Instead, the thermal efficient electrical assembly can further include a metal element that is electrically insulated from the electrical component and thermally communicates with it, and the metal thermal bridge is in direct contact with both the metal element and the heat sink layer. ..

The electrically insulated metal element can provide an equivalent thermal mooring for the component without a specific thermal pad. Therefore, a good thermal path can be provided from this metal element.

Preferably, the metal element can be a copper element, but optionally the thermal bridge can directly and electrically communicate with the negative electrodes of the electrical component. The latter configuration can be used to provide an optimal thermal path when the heat sink does not need to be completely electrically insulated. For example, if the heat sink layer is not in contact with any other component and is not accessible to the user, then no insulation is needed.

Preferably, the electrical component can be a light emitting diode. Conveniently, light emitting diodes generally convert 60% to 95% of their electrical energy into heat, but their heat dissipation properties are insufficient to effectively lower the temperature. Therefore, light emitting diodes generally rely on heat sinks to provide the required heat transfer characteristics. This configuration is particularly effective when used with such components.

According to the second aspect of the present invention, a conductive layer forming a part of a flexible printed circuit board including a flexible substrate, a heat insulating layer, and an electrically insulating interconnect layer inserted between the conductive layer and the heat insulating layer. An electrical component that electrically communicates with the conductive layer and a metal thermal bridge that thermally communicates with the electrical component and is in direct contact with the sheet sink layer are provided, and the electrically insulating interconnect layer is provided by the metal thermal bridge. A flexible circuit with high thermal efficiency that bypasses is provided.

According to a third aspect of the present invention, a lighting component including a flexible circuit having high thermal efficiency according to the second aspect of the present invention is provided, and the electric component is a light emitting diode.

According to a fourth aspect of the present invention, there is provided a method for efficiently transferring heat from an electrical component to a heat sink, which method a) prepares an electrical component that electrically communicates with the conductive layer and the heat sink layer. Then, the steps in which the insulating interconnect layer is provided between them, and b) the electrical component and the heat sink layer are thermally communicated to the electrical component and thermally contacted to the metal thermal bridge in direct contact with the heat sink layer. It comprises steps to interconnect and bypass the electrically insulating interconnect layer.

Hereinafter, the present invention will be described in detail exemplary with reference to the accompanying drawings.

A first embodiment of an electric assembly having high thermal efficiency according to the first aspect of the present invention is shown. A second embodiment of an electric assembly having a high thermal efficiency according to the first aspect of the present invention without a substrate layer is shown. A third embodiment of a thermally efficient electrical assembly according to a first aspect of the present invention, comprising metal elements and solder rivets, is shown. A fourth embodiment of an electrical assembly with high thermal efficiency according to the first aspect of the present invention, in which solder rivets are connected to negative electrodes of electrical components, is shown.

First, with reference to FIG. 1, a first embodiment of the thermally efficient electrical assembly 100 of the present invention is shown. A cross-sectional view through the circuit board assembly 102 is shown, wherein the relationship between the electrical component 104, which is a light emitting diode or LED 106, and the heat sink layer 108 is described in detail.

In this embodiment, the LED 106 is attached to the conductive layer 112 with two electrodes 110, which can be any other material that can carry current, such as copper track or silver. LED mounting is accomplished using the solder connector 114. The conductive layer 112 itself is attached to a flexible substrate layer 116 such as a polyimide film. This attachment can be conveniently done by using the electrically insulating adhesive layer 118a. The adhesive layer 118a is preferably an electrically insulating or highly resistant adhesive in order to prevent or limit the electrical conduction from the conductive layer 112 to the flexible substrate layer 116. An electrically insulating adhesive layer 118a is preferred, but any other electrically insulating or electrically resistant interconnect layer can be used instead. The flexible substrate layer 116 allows the entire assembly 100 to flex as needed while imparting additional strength to the conductive layer 112. Therefore, this embodiment can be used when it is required to flexibly fit the electrical assembly 100 into an enclosure such as a car headlight housing.

Flexible assemblies are disclosed, but the present invention can also be used in conjunction with non-flexible circuits. Such non-flexible circuits can include a silicon-based substrate layer, a glass fiber reinforced epoxy resin laminate layer such as FR4, or other layers with limited flexibility or inflexibility. Such features do not impair the concept of the invention described in the claims.

Another adhesive layer 118b is arranged between the flexible substrate layer 116 and the heat sink layer 108. The heat sink layer 108 itself includes upper and lower heat sink sublayers 120a and 120b. The upper heat sink sublayer 120a in this embodiment is preferably made of copper. Copper can be advantageously bonded to solder, the advantages of which are clarified below. The lower heat sink sublayer 120a can be conveniently formed of aluminum, which is a lightweight and heat-energy-friendly conductor, while generally at a lower cost than copper. The upper and lower heat sink sublayers 120a and 120b can be manufactured together by, for example, hot rolling.

However, other combinations of materials can be used in place of the materials described in this embodiment. Similarly, a heat sink layer formed of only one layer can be provided, the single layer of which can be copper, aluminum, or any other material capable of suitable heat transfer.

Further, the LED 106 includes a thermal pad 122 and is electrically insulated from the electrode 110 of the LED 106. In this embodiment, the thermal pad 122 is directly connected to the heat sink layer 108 via the metal thermal bridge 124, and more specifically to the upper heat sink sublayer 120a. The metal thermal bridge 124 is a solder column 126. Therefore, a direct metal heat path is provided for direct heat transfer or conduction from the electrical component 104 to the heat sink layer 108.

Also, the thermal pad 122 is conveniently made of copper. Copper is a very good thermal conductor and forms a strong bond with the solder, which is advantageous for the structure. Therefore, no intermediate material is required to interconnect the thermal bridge 124 with the thermal pad 122 and the heat sink layer 108.

In this embodiment, the use of the electrically insulating thermal pad 122 ensures that the heat sink layer 108 remains electrically isolated from the LED 106. Therefore, the heatsink layer 108 does not need to be isolated from the surrounding housing or other attachments, significantly reducing the risk of electric shock resulting from contact with the heatsink. In addition, the thermal pad 122 is specifically arranged and designed to maximize heat conduction away from the LED 106, ensuring the efficiency of this configuration.

On top of each portion of the conductive layer 112, it may be preferable to include a cover layer 128 which is a protective coating layer and provides some level of protection to the underlying layer. Such a cover layer 128 can be formed of polyimide, polyester, or other suitable material and can be attached to the conductive layer 112 via an adhesive. Conveniently, the cover layer 128 provides flexible protection against other layers, which allows the circuit board assembly 102 to flex as desired. The cover layer 128 and the adhesive 118c can be pressed onto the required surface, for example. Alternatively, a solder resist can be used instead of the cover layer 128.

Further, by applying the stiffener 130, it is possible to locally harden each part of the flexible circuit board assembly 102. The stiffener 130 has a thickness generally in the range of 0.050 mm to 2.400 mm and can be formed of a material such as FR4, polyimide, or polyester. Similarly, the adhesive 118d can be used to bond the stiffener 130 to the other layers of the assembly 102. By making each part of the assembly 102 rigid, the strength characteristics can be enhanced as needed, and the life of the structure is extended, especially in a relatively harsh operating environment.

Compared to the stiffener 130, the flexible substrate layer 116 and the cover layer 128 can generally be manufactured with a thickness of 0.012 mm to 0.125 mm. Similarly, the thickness of the adhesive 118ad is 0.012 mm to 0.050 mm. These thickness ranges are merely exemplary and are specific for use in such circuits, and the scope of the invention is not necessarily intended to be limited to the use of layers of these thicknesses.

Therefore, the configuration of the thermal-efficient electrical assembly 100 provides a path for the transfer or conduction of thermal energy from the electrical component 104 to the heat sink layer 108. In known configurations, heat is typically dissipated from component 104 through intervening layers to heat sink layer 108 instead. In many of these layers, such as the layer used as the adhesive 118ad or for the flexible substrate layer 116, heat tends not to be transferred through that layer to the lower layers, but rather more rapidly in the plane of the material. There is. Therefore, by replacing this inefficient heat path with a more efficient thermal bridge 124 that bypasses these layers, heat transfer from the electrical component 104 can be increased, which is effective for the operation of the component 104 and the circuit itself. Can be.

FIG. 2 shows a second embodiment 200 of an electric assembly having high thermal efficiency, and the assembly 200 is simplified. Details of similar or identical features in this embodiment and other embodiments are omitted for brevity.

The electrical component 204, also represented as LED 206, is similarly coupled to the heat sink layer 208 by a thermal bridge 224. However, the height of the thermal bridge 224 is lower than the height of the first embodiment due to the omission of the flexible substrate layer. Therefore, in this second embodiment, the layer of the electrical assembly 200 is limited to the conductive layer 212 coated with the adhesive 218c and the cover layer 228, and is adhered to the heat sink layer 208 by the adhesive layer 218. If necessary, the stiffener 230 is attached using adhesive 218d.

The flexible substrate layer can be omitted if it is not necessary to provide additional strength, and the conductive layer 212 and the cover layer 228 are sufficient to provide both the thermal efficiency electrical assembly 200 with both strength and flexibility. Is.

However, due to the reduced thickness of the electrical assembly 200 and the associated reduced height of the thermal bridge 224, the heat transfer between the LED 206 and the heat sink layer 208 is further enhanced in the embodiment of FIG. be able to.

FIG. 3 shows a third embodiment 300 of an electrical assembly having high thermal efficiency, which comprises an electrical component 304 that does not include a thermal pad. The electrical assembly 300 includes a conductive layer 312 on which the electrical components 304 are mounted. In the present embodiment, the electrically insulated metal element 332, which is also formed of copper, is adjacent to the conductive layer 312, but is formed separately from the conductive layer 312. Similarly, reference numbers similar to the first and second embodiments refer to the same or similar components and are not described in detail for brevity.

The metal element 332 is electrically insulated, but is thermally coupled to the conductive layer 312, and thus to the electrical component 304. The thermal bridge 324 is formed here as solder rivets 334 and provides a direct metal connection between the metal element 332 and the heat sink layer 308. Therefore, the thermal bridge 324 penetrates the flexible substrate layers 316 and the adhesive layers 318a and 318b arranged between them to provide a thermal bypass to the heat sink layer 308.

The metal element 332 is thermally bonded to the conductive layer 312 by the heat bonding portion 336. The thermal coupling portion 336 is formed here as part of the cover layer 328, but may otherwise be formed of any other material that provides thermal conduction and electrical insulation properties. The extended distance of the thermal coupling portion 336 is smaller than the distance between the electrical component 304 and the heat sink layer 308, limiting resistance to heat transfer with high thermal efficiency. Therefore, the third embodiment 300 of the electric assembly having high thermal efficiency is still an improvement beyond the conventionally known configuration.

The thermally efficient electrical assembly 400 of the fourth embodiment shown in FIG. 4 is largely similar to FIG. 3, but without metal elements or thermal couplings, and thus between the thermal bridge 424 and the heat sink layer 408. There is no separation. Therefore, there is less resistance to heat conduction than in the third embodiment. As mentioned above, reference numbers similar to the embodiments described above refer to the same or similar components and are not described in detail for the sake of brevity.

Preferably, the thermal bridge 424 is attached to the negative electrode 410a of the electrical component 404 to receive a voltage lower than the positive electrode 410b. However, when the thermal bridge 424 is so connected, the heat sink layer 408 can also receive an increased voltage.

Conveniently, this configuration does not have the thermal coupling portion 336, so that the thermal efficiency can be higher than that of the third embodiment. However, since the heat sink layer 408 and the thermal bridge 424 are electrically connected to the conductive layer 412, it is preferably necessary to electrically insulate them from other parts of the assembly 400 during use. For example, in the case of an automobile, it is necessary to electrically insulate the headlight housing from the headlight housing in order to prevent accidental electric shock of a person who touches the headlight housing.

Although the above embodiments have been described in relation to LEDs, any other electrical component can be used in conjunction with a thermal efficient electrical assembly. The assembly is most advantageous when used with electrical components with high heat output such as LEDs, transformers, or other components, but is beneficial for any electrical component that dissipates heat to the circuit. Impact is expected.

Moreover, the inventions of the present disclosure need not be used with flexible circuits. Non-flexible circuits can also benefit from this configuration, the only difference being the component layers of the circuit board, for example, the flexible substrate layer is replaced by the non-flexible substrate layer. The basic concept of a thermal bridge that bypasses the intermediate layer of the circuit board remains unchanged. Conveniently, any substrate layer can be insulating to allow for enhanced electrical insulation properties.

Thus, it is possible to have a metallic thermal bridge that provides good heat transfer between the electrical components and the heat sink layer, and the metallic thermal bridge can provide a thermally efficient electrical assembly that bypasses any intervening layers. Is.

The terms "equipped / equipped" and "have / include" as used herein with respect to the present invention identify the presence of the described features, completeness, steps, or components. Used for, but does not preclude the existence or addition of one or more features, perfections, steps, components, or groups thereof.

Also, certain features of the invention described in relation to separate embodiments for clarity can be provided in combination with a single embodiment. Conversely, the various features of the invention described in relation to a single embodiment for brevity can also be provided separately or in any suitable partial combination.

The above embodiments are merely exemplary, and various other modifications will be apparent to those skilled in the art without departing from the scope of the invention described and defined herein.

100 Thermally efficient electrical assembly 102 Circuit board assembly 104 Electrical components 106 Light emitting diode or LED
108 Heat sink layer 110 Electrode 112 Conductive layer 114 Solder connector 116 Flexible substrate layer 116
118a-d Electrically insulating adhesive layer 120a Upper heat sink sub-layer 120b Lower heat sink sub-layer 122 Thermal pad 124 Metal thermal bridge 126 Solder column 128 Cover layer 130 Stiffener

Claims (7)

An electrical assembly with high thermal efficiency that includes a conductive layer and a heat sink layer.
An electrically insulating interconnect layer inserted between the conductive layer and the heat sink layer,
Electrical components that electrically communicate with the conductive layer,
A metallic thermal bridge for direct contact with the electrical component and in thermal communication and the heat sink layer,
With
Bypassing the electrically insulating interconnect layer with a metal thermal bridge
The heat sink layer includes upper and lower heat sink sublayers, the upper heat sink sublayer is adhered to the conductive layer, the upper heat sink sublayer is made of copper, and the lower heat sink sublayer is made of aluminum. ,
The metal thermal bridge comes into contact with the heat sink layer from one side of the electrical component through the electrically insulating interconnect layer, and is further electrically insulated from the two electrodes of the electrical component and the electricity. The metal thermal bridge comprises a metal element that thermally communicates with the component, the metal thermal bridge is in direct contact with both the metal element and the upper heat sink sublayer of the heat sink layer, and the metal thermal bridge is a solder column. Is,
Thermally efficient electrical assembly. The electrical assembly according to claim 1, wherein the electrically insulating interconnect layer is an electrically insulating adhesive layer. The highly thermally efficient electrical assembly according to claim 1, wherein the conductive layer is further adhered to a substrate layer. The highly thermally efficient electrical assembly according to claim 3, wherein the substrate layer contains polyimide. The highly thermally efficient electrical assembly according to claim 1, wherein the metal thermal bridge is a solder rivet. The highly thermally efficient electrical assembly according to claim 1, wherein the metal element is a copper element. The highly thermally efficient electrical assembly according to claim 1, wherein the electrical component is a light emitting diode.

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